> Now seriously Jinx, wouldn't a proper cruise control
> need to be closed-loop to airspeed, ie monitored by GPS
> and adjusted accordingly? If you do it closed-loop to
> engine revs how useful can it be? Isn't it just a slightly
> improved throttle and really how bad is the stock
> throttle anyway? Doesn't it hold the revs constant

I'll quote you from Bob Japundza's post of a few days ago

"The advantage of a constant-speed propeller over a fixed
pitch propeller is akin to the difference between a transmission
with only one gear ratio and one that has a variable speed drive.
They outperform fixed-pitch props on several orders of magnitude.
You can always maintain an efficient RPM for climb or cruise
so the prop can absorb the most power in a given flight regime
without "loading" the engine.  With a fixed-pitch prop, the RPM
varies with the airspeed of the aircraft, so if you pull the nose up
the RPM will drop or if you point the nose down you can
overspeed the engine"

http://www.spa-training.com/constant_speed_props.htm

The propellors I'll be working with are 4-blade, with a planetary
gear driven by a DC motor to adjust the pitch. There are micro
switches at the limits too. According to others on the list and Mr
X himself, it is not all difficult. Mr X has no concerns about safety
either - he has a make-do governor built around a stepper on a
plane now that doesn't work half the time and he's quite relaxed,
even a little nonchalant, about it. The worst that can happen is
that the pilot simply takes over manually. I've been told that some
units available now cost around NZ$1500 and have unused and
unnecessary features which is encouraging

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